Water is more dense than air. Carl experienced the effects of that increased weight (density) first-hand when he began his deep-sea diving career.

Whenever a human being dives underwater, pressure on the body intensifies. Increased pressure causes changes to the air gases (oxygen and nitrogen ) a person inhaled at the surface. The deeper the dive, the greater the changes in the inhaled air gases and the potential for problems. A common ailment is "the bends" - named for the way people bend due to pain. But a diver can also sustain fatal injuries from conditions much worse than the bends.

Although oxygen is necessary to sustain human life, people actually breathe in a much greater percentage of nitrogen (78% compared to 21% oxygen)) from the surrounding air. Nitrogen (the culprit behind the bends) is inert (it doesn’t do anything) in a non-diving body. But during a deep-dive, nitrogen causes bubbles to form in a body under pressure in the same way as carbon dioxide causes bubbles to form in Coca Cola when it is under pressure.

Nitrogen, under deep-sea pressure, can also impair a diver’s judgment in a condition called nitrogen narcosis (or "rapture of the deep"). A person who has nitrogen narcosis often acts like a person who is intoxicated. "Rapture of the deep" can cause a diver to do completely unexpected and unsafe things. And, although we don’t think about it unless we’re deep-sea divers, oxygen at depth can actually poison a human body if it isn’t diluted with other gases. That potentially fatal condition is called oxygen toxicity.

Fortunately, Carl Brashear never sustained any of these injuries in his quest to become the Navy’s first black master diver.